Touch panel

ABSTRACT

A touch sensor (touch panel) which can be formed over the same substrate as a display portion is provided. Alternatively, a touch sensor (touch panel) which does not cause degradation in the quality of an image displayed on a display portion is provided. The touch panel includes a light-emitting element and a microstructure in which a pair of electrodes facing each other is isolated with an insulating material. As the insulating material, an elastic material or a material having a hole is used so that a filler layer formed using the insulating material can be deformed when a movable portion operates. It is preferable to use a material which is softened or hardened by certain treatment (e.g., heat treatment or chemical treatment) after formation.

This application is a continuation of copending U.S. application Ser.No. 12/788,893, filed on May 27, 2010 which is incorporated herein byreference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to touch panels including touch sensorsand display portions.

2. Description of the Related Art

In recent years, display devices including touch sensors have attractedattention. The display devices including touch sensors are referred toas touch panels, touch screens, or the like (hereinafter simply referredto as touch panels). Examples of the types of touch sensors include aresistive type, an acoustic pulse recognition type, a surface acousticwave type, an infrared light-blocking type, a capacitive type, anelectromagnetic induction type, an image recognition type, and the like.These types have different operating principles. In any type of touchsensor, data can be input when an object to be detected is in contactwith a display device.

A conventional touch sensor is formed over or below an EL layerincluding a light-emitting layer. In the case where a touch sensor isformed over an EL layer as in Reference 1, it is necessary to provide aprotective film or a protective substrate over a display surface. Thus,even if any high-definition display device is manufactured, visibilitydecreases and image quality degrades. In contrast, in the case where atouch sensor is formed below an EL layer as in Reference 2, an image canbe displayed at high definition; however, it is difficult to applypressure to the touch sensor. Thus, the touch sensor has a problem ofthe decrease in accuracy.

REFERENCE

Reference 1: Japanese Published Patent Application No. 2000-331557

Reference 2: Japanese Published Patent Application No. 2003-296022

SUMMARY OF THE INVENTION

It is an object of one embodiment of the present invention to provide atouch sensor which can be formed over the same substrate as a displayportion. Alternatively, it is an object of one embodiment of the presentinvention to provide a touch sensor which does not cause degradation inthe quality of an image displayed on a display portion.

In one embodiment of the present invention, a touch panel includes amicrostructure, a thin film transistor, a light-emitting element whichis electrically connected to the thin film transistor, and a spacer. Themicrostructure includes a lower electrode, an upper electrode whichfaces the lower electrode and can move in a direction to the lowerelectrode by application of pressure, and a filler layer which isprovided between the lower electrode and the upper electrode. The lowerelectrode is formed using the same material as a gate electrode of thethin film transistor. The upper electrode is formed using the samematerial as a first electrode of the light-emitting element. The fillerlayer is formed using a porous insulating material which can bereversibly deformed by the pressure. The spacer is formed over the upperelectrode with the use of a material which is harder than the materialof a partition wall for covering the first electrode of thelight-emitting element. The partition wall is formed using a materialwhich is harder than the material of the filler layer.

In one embodiment of the present invention, a touch panel includes amicrostructure, a thin film transistor, a light-emitting element whichis electrically connected to the thin film transistor, and a spacer. Themicrostructure includes a lower electrode, an upper electrode whichfaces the lower electrode and can move in a direction to the lowerelectrode by application of pressure, and a filler layer which isprovided between the lower electrode and the upper electrode. The lowerelectrode is formed using the same material as a source electrode or adrain electrode of the thin film transistor. The upper electrode isformed using the same material as a first electrode of thelight-emitting element. The filler layer is formed using a porousinsulating material which can be reversibly deformed by the pressure.The spacer is formed over the upper electrode with the use of a materialwhich is harder than the material of a partition wall for covering thefirst electrode of the light-emitting element. The partition wall isformed using a material which is harder than the material of the fillerlayer.

The porosity of the filler layer is preferably higher than or equal to20% and lower than or equal to 80%.

The porous insulating material is preferably formed using a blockcopolymer.

In one embodiment of the present invention, a touch panel includes amicrostructure, a thin film transistor, a light-emitting element whichis electrically connected to the thin film transistor, and a spacer. Themicrostructure includes a lower electrode, an upper electrode whichfaces the lower electrode and can move in a direction to the lowerelectrode by application of pressure, and a filler layer which isprovided between the lower electrode and the upper electrode. The lowerelectrode is formed using the same material as a gate electrode of thethin film transistor. The upper electrode is formed using the samematerial as a first electrode of the light-emitting element. The fillerlayer is formed using an elastic insulating material which can bereversibly deformed by the pressure. The spacer is formed over the upperelectrode with the use of a material which is harder than the materialof a partition wall for covering the first electrode of thelight-emitting element. The partition wall is formed using a materialwhich is harder than the material of the filler layer.

In one embodiment of the present invention, a touch panel includes amicrostructure, a thin film transistor, a light-emitting element whichis electrically connected to the thin film transistor, and a spacer. Themicrostructure includes a lower electrode, an upper electrode whichfaces the lower electrode and can move in a direction to the lowerelectrode by application of pressure, and a filler layer which isprovided between the lower electrode and the upper electrode. The lowerelectrode is formed using the same material as a source electrode or adrain electrode of the thin film transistor. The upper electrode isformed using the same material as a first electrode of thelight-emitting element. The filler layer is formed using an elasticinsulating material which can be reversibly deformed by the pressure.The spacer is formed over the upper electrode with the use of a materialwhich is harder than the material of a partition wall for covering thefirst electrode of the light-emitting element. The partition wall isformed using a material which is harder than the material of the fillerlayer.

The elastic insulating material is preferably formed using an elastomeror a thermoplastic elastomer.

In one embodiment of the present invention, a touch sensor and alight-emitting element are disposed, so that it is possible to provide athin touch panel with little degradation in image quality.

In one embodiment of the present invention, by using materials havingdifferent hardness for a filler layer, a partition wall, and a spacer,it is possible to provide a touch panel where data can be inputefficiently and pressure is not applied to a light-emitting elementeasily. Further, by providing a spacer above a touch sensor, durabilityand sensitivity of the touch sensor can be improved.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings:

FIGS. 1A and 1B are cross-sectional views according to one embodiment ofthe present invention;

FIG. 2 is a cross-sectional view according to one embodiment of thepresent invention;

FIGS. 3A and 3B are circuit diagrams according to one embodiment of thepresent invention;

FIG. 4 is a diagram illustrating a position detection method accordingto one embodiment of the present invention;

FIGS. 5A and 5B are circuit diagrams according to one embodiment of thepresent invention;

FIG. 6 is a diagram illustrating a position detection method accordingto one embodiment of the present invention;

FIGS. 7A to 7G are diagrams each illustrating a block copolymeraccording to one embodiment of the present invention;

FIG. 8 is a top view according to one embodiment of the presentinvention;

FIG. 9 is a top view according to one embodiment of the presentinvention;

FIG. 10 is a top view according to one embodiment of the presentinvention;

FIG. 11 is a top view according to one embodiment of the presentinvention;

FIG. 12 is a top view according to one embodiment of the presentinvention;

FIG. 13 is a top view according to one embodiment of the presentinvention;

FIG. 14 is a top view according to one embodiment of the presentinvention;

FIGS. 15A to 15C are cross-sectional views according to one embodimentof the present invention;

FIG. 16 is a cross-sectional view according to one embodiment of thepresent invention;

FIG. 17 is a cross-sectional view according to one embodiment of thepresent invention;

FIG. 18 is a top view according to one embodiment of the presentinvention;

FIG. 19 is a top view according to one embodiment of the presentinvention;

FIG. 20 is a top view according to one embodiment of the presentinvention;

FIG. 21 is a top view according to one embodiment of the presentinvention;

FIG. 22 is a top view according to one embodiment of the presentinvention;

FIG. 23 is a top view according to one embodiment of the presentinvention;

FIG. 24 is a top view according to one embodiment of the presentinvention;

FIGS. 25A to 25C are cross-sectional views according to one embodimentof the present invention;

FIG. 26 is a cross-sectional view according to one embodiment of thepresent invention;

FIG. 27 is a cross-sectional view according to one embodiment of thepresent invention; and

FIGS. 28A and 28B are external views according to one embodiment of thepresent invention.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, embodiments of the present invention will be described indetail with reference to the drawings. Note that the present inventionis not limited to the following description. It will be readilyappreciated by those skilled in the art that modes and details of thepresent invention can be changed in various ways without departing fromthe spirit and scope of the present invention. Therefore, the presentinvention should not be construed as being limited to the followingdescription of the embodiments. Note that in the following structures ofone embodiment of the present invention, the same portions or portionshaving similar functions are denoted by common reference numerals indifferent drawings, and description thereof is not repeated.

Embodiment 1

In this embodiment, structures of a touch panel of one embodiment of thepresent invention are described with reference to FIGS. 1A and 1B andFIG. 2.

A touch sensor is a device to which data is input when an upperelectrode and a lower electrode are in contact with each other or thedistance between the upper electrode and the lower electrode is changed,for example. In one embodiment of the present invention, amicroelectromechanical system (MEMS) is used for the touch sensor.

MEMS is the abbreviation of a microelectromechanical system and is alsosimply called a micromachine. A micromachine generally refers to a microdevice where “an electronic circuit having a semiconductor element” and“a movable microstructure having a three-dimensional structure” formedusing a semiconductor microfabrication technology are integrated. Unlikethe semiconductor element, the microstructure generally includes amovable portion.

The microstructure includes a structural layer and a hollow portion, andthe structural layer includes a movable portion. Since the movableportion of the structural layer operates, sufficient mechanical strengthis needed for the microstructure. A conventional microstructure includesa hollow portion in order to secure an operation region of a movableportion. The hollow portion is formed in such a manner that asacrificial layer is formed in a portion which is to be the hollowportion and is removed by etching or the like after a structural layeror the like is formed. For example, in the case of a microstructure inwhich a movable portion of a structural layer operates in a directionperpendicular to a substrate surface, a lower part of the microstructureis formed, a sacrificial layer is formed over the lower part of themicrostructure, an upper part of the microstructure is formed over thesacrificial layer, and the sacrificial layer is removed by etching orthe like. In this manner, a microstructure including a hollow portion isformed.

However, when a hollow portion is formed using a sacrificial layer asdescribed above, there is a problem in that a microstructure is easilydamaged or broken due to strong contact between an upper electrode and alower electrode of the microstructure in a manufacturing process, forexample. Further, there is a problem in that normal operation cannot beperformed due to sticking between an upper electrode and a lowerelectrode. Here, sticking refers to a phenomenon in which, due to theoperation of a movable portion of a microstructure, an upper electrodeand a lower electrode are in strong contact with each other such thatthe upper electrode and the lower electrode cannot separate from eachother.

Further, when a hollow portion is formed using a sacrificial layer,there is a problem in that the sacrificial layer is not completelyetched and an etching residue is generated. Alternatively, because ofthe operation of an upper portion of a formed microstructure, themicrostructure might be damaged or broken. This is particularlyremarkable when the height of the hollow portion is high or thetoughness of a structural layer is not enough. Furthermore, when ahollow portion is provided, there is a problem in that a structureincluding the hollow portion is deformed by, for example, warpage andthat a desired structure cannot be obtained.

Thus, a microstructure (MEMS) used in one embodiment of the presentinvention has a structure where a pair of electrodes facing each otheris isolated with a space, a movable structure is provided with at leastone of the electrodes, and the space is filled with an insulatingmaterial. As the insulating material, a material having a hole is usedso that a filler material layer formed using the insulating material canbe deformed when a movable portion operates. It is preferable to use amaterial which is softened or hardened by certain treatment (e.g., heattreatment or chemical treatment) after formation.

FIGS. 1A and 1B are cross-sectional views schematically illustrating atouch panel of one embodiment of the present invention.

A base film 101 and a thin film transistor 102 are formed over asubstrate 100. The thin film transistor 102 includes, for example, agate electrode 103, a gate insulating film 104, a first semiconductorlayer 105, second semiconductor layers (a semiconductor layer 106 and asemiconductor layer 107), a conductive layer 108, and a conductive layer109. In FIGS. 1A and 1B, a lower electrode 110 of a touch sensor isformed using the same material as the conductive layer 108 and theconductive layer 109. The lower electrode 110 may be formed using anyone of materials used for the thin film transistor 102. However, thematerial used for the lower electrode 110 is not limited to the abovematerial.

An insulating layer 111 is formed so as to cover the thin filmtransistor 102. A filler layer 112 is formed over the lower electrode110 of the touch sensor. A wiring 114 which electrically connects afirst electrode 113 of an EL element and the conductive layer 108 toeach other is formed. An upper electrode 115 of the touch sensor isformed using the same material as the first electrode 113. Note that adeformable porous material or an elastic insulating material can be usedfor the filler layer 112. Further, the first electrode 113 and thewiring 114 can be formed concurrently using the same material.

As illustrated in FIG. 1A, the filler layer 112 may have a swollen upperportion. Alternatively, as illustrated in FIG. 1B, the filler layer 112may have a flat upper portion.

In addition, a partition wall 116 which covers an end portion of thefirst electrode 113 and the upper electrode 115 and has an openingreaching the upper electrode 115 is formed. A spacer 117 is formed inthe opening. The spacer 117 is provided so as to overlap with the lowerelectrode 110 and the filler layer 112 with the upper electrode 115therebetween. An EL layer 118 is formed in contact with the firstelectrode 113. A second electrode 119 is formed over the EL layer 118and the partition wall 116.

Here, among the materials used for the filler layer 112, the partitionwall 116, and the spacer 117, the material used for the spacer 117 isthe hardest material and the material used for the filler layer 112 isthe softest material. Elastic modulus or the like indicates hardness orsoftness. The elastic modulus is a physical value indicating an object'stendency to be deformed elastically. In the case where hardness orsoftness is indicated by elastic modulus, the elastic modulus of thematerial used for the spacer 117 is higher than the elastic modulus ofthe material used for the partition wall 116, and the elastic modulus ofthe material used for the partition wall 116 is higher than the elasticmodulus of the material used for the filler layer 112.

Then, sealing is performed. For example, sealing is performed in such amanner that a sealant (not illustrated) is provided at an end portion ofan element substrate 120 including the thin film transistor 102 and thelike and the element substrate 120 and a sealing substrate 121 areattached to each other with the sealant. The touch panel illustrated inFIGS. 1A and 1B has a structure where a light-emitting element faces aspace 122 surrounded by the element substrate 120, the sealing substrate121, and the sealant. The space 122 is filled with an inert gas (e.g.,nitrogen or argon). The space 122 may be filled with a sealant as asubstitute for the inert gas.

Next, FIG. 2 illustrates the case where the touch panel is touched witha finger.

As illustrated in FIG. 2, when a surface of the sealing substrate 121 istouched with a finger 123, the sealing substrate 121 bends. In thiscase, an upper portion of the partition wall 116 is pressed and dented,and the spacer 117 which is harder (which has higher elastic modulus)than the material used for the partition wall 116 is pressed down. Sincethe filler layer 112 provided below the spacer 117 is softer (has lowerelastic modulus) than the spacer 117, the spacer 117 is pressed downwithout deformation. Since the upper electrode 115 of the touch sensoris pressed down when the spacer 117 is pressed down, the lower electrode110 and the upper electrode 115 of the touch sensor are in contact witheach other or the distance between the lower electrode 110 and the upperelectrode 115 is changed. Thus, data can be input.

According to one embodiment of the present invention, a touch sensor anda light-emitting element are disposed, so that it is possible to providea thin touch panel with less degradation in image quality as compared tothe case where a touch sensor is provided above or below alight-emitting element.

According to one embodiment of the present invention, by using materialshaving different hardness for a filler layer, a partition wall, and aspacer, it is possible to provide a touch panel where data can be inputefficiently and pressure is not applied to a light-emitting elementeasily. Further, by providing a spacer above a touch sensor, durabilityand sensitivity of the touch sensor can be improved.

Note that this embodiment can be combined with the structure describedin any of the other embodiments in this specification as appropriate.

Embodiment 2

In this embodiment, the operation of a capacitive type touch panel isdescribed.

In a capacitive type touch sensor, data is input when the distancebetween an upper electrode and a lower electrode is changed. In oneembodiment of the present invention, a microstructure (MEMS) is used forthe touch sensor.

Since the structure of the touch sensor is as illustrated in FIGS. 1Aand 1B and FIG. 2, description thereof is omitted here.

In the capacitive type touch panel, an insulating material which is adielectric is provided between an upper electrode and a lower electrode.A deformable porous material or an elastic insulating material is usedfor the filler layer 112, which is the dielectric.

FIG. 3A illustrates one embodiment of one pixel included in thecapacitive type touch panel. A top view of FIG. 3A is illustrated inFIG. 12 or FIG. 22, for example.

A gate of a switching transistor 200 is electrically connected to a gateline 201. One of a source and a drain of the switching transistor 200 iselectrically connected to a source line 202. A first terminal of a firstcapacitor 203 is electrically connected to the other of the source andthe drain of the switching transistor 200. A second terminal of thefirst capacitor 203 is electrically connected to a power supply line204. A gate of a driving transistor 205 is electrically connected to theother of the source and the drain of the switching transistor 200. Oneof a source and a drain of the driving transistor 205 is electricallyconnected to one of electrodes of a light-emitting element 206. Theother of the electrodes of the light-emitting element 206 iselectrically connected to a power supply line 207. The other of thesource and the drain of the driving transistor 205 is electricallyconnected to the power supply line 204. A first terminal of a secondcapacitor 208 is electrically connected to the power supply line 204. Asecond terminal of the second capacitor 208 is electrically connected toa column line 209. A first terminal of a third capacitor 210 iselectrically connected to the power supply line 204. A second terminalof the third capacitor 210 is electrically connected to a row line 211.Note that each of the second capacitor 208 and the third capacitor 210is a capacitor whose capacitance value is changed when the touch panelis touched with a finger or the like. Although a p-channel transistor isillustrated as the driving transistor 205 here, an n-channel transistormay be used.

FIG. 4 illustrates column lines (lines for detecting x coordinates) androw lines (lines for detecting y coordinates) for detecting a positionwhere the touch panel is touched with a finger or the like. The columnline 209 is any one of x1 to xn (n is an integer of 1 or more)illustrated in FIG. 4. The row line 211 is any one of y1 to ym (m is aninteger of 1 or more) illustrated in FIG. 4.

The touch sensor includes an upper electrode, a dielectric (a fillerlayer in one embodiment of the present invention), and a lowerelectrode. The capacitance value of the touch sensor is determined bythe dielectric constant of a material used for the filler layer, thearea of the upper electrode or the lower electrode, and the distancebetween the upper electrode and the lower electrode. When the distancebetween the upper electrode and the lower electrode is decreased, thecapacitance value is increased. When the distance between the upperelectrode and the lower electrode is increased, the capacitance value isdecreased.

Further, the amount of electric charges accumulated in the touch sensoris obtained by multiplying the capacitance value by the voltage betweenthe upper electrode and the lower electrode. Since the voltage betweenthe upper electrode and the lower electrode is not changed, the amountof the electric charges accumulated in the touch sensor is changed whenthe capacitance value is changed by change in the distance between theupper electrode and the lower electrode. Since current flows through thecolumn line 209 and the row line 211 when the amount of the electriccharges is changed, a touch position 251 can be detected by provision ofa detector (detection circuit) 250 in a position through which currentflows.

In the capacitive type touch panel, data is input when the distancebetween the upper electrode and the lower electrode is changed. Thus,data can be input with light touch.

Note that this embodiment can be combined with the structure describedin any of the other embodiments in this specification as appropriate.

Embodiment 3

In this embodiment, the operation of a capacitive type touch panel whichis different from that in Embodiment 2 is described.

FIG. 3B illustrates one embodiment of one pixel included in thecapacitive type touch panel. A top view of FIG. 3B is illustrated inFIG. 13 or FIG. 23, for example.

The switching transistor 200, the gate line 201, the source line 202,the first capacitor 203, the power supply line 204, the drivingtransistor 205, the light-emitting element 206, and the power supplyline 207 are similar to those in FIG. 3A. A first terminal of a secondcapacitor 212 is electrically connected to the power supply line 204. Asecond terminal of the second capacitor 212 is electrically connected toa column line 213. The column line 213 is electrically connected to arow line 214.

Although two capacitors (touch sensors) whose capacitance values arechanged are provided in FIG. 3A, one capacitor (touch sensor) whosecapacitance value is changed is provided in FIG. 3B. A column line (aline for detecting an x coordinate) and a row line (a line for detectinga y coordinate) for detecting a position where the touch panel istouched with a finger or the like are electrically connected to eachother. Therefore, although the touch position is detected by the xcoordinate and the y coordinate individually in the structure of FIG.3A, the x coordinate and the y coordinate are detected with one touchsensor in the structure of FIG. 3B.

In the capacitive type touch panel, data is input when the distancebetween the upper electrode and the lower electrode is changed. Thus,data can be input with light touch.

Note that this embodiment can be combined with the structure describedin any of the other embodiments in this specification as appropriate.

Embodiment 4

In this embodiment, the operation of a resistive type touch panel isdescribed.

In a resistive type touch sensor, data is input when an upper electrodeand a lower electrode are in contact with each other. In one embodimentof the present invention, a microstructure (MEMS) is used for the touchsensor.

Since the structure of the touch sensor is as illustrated in FIGS. 1Aand 1B and FIG. 2, description thereof is omitted here.

In the resistive type touch panel, an insulating material is providedbetween an upper electrode and a lower electrode. A deformable porousmaterial or an elastic insulating material is preferably used for thefiller layer 112.

FIG. 5A illustrates one embodiment of one pixel included in theresistive type touch panel. A top view of FIG. 5A is illustrated in FIG.12 or FIG. 22, for example.

A gate of a switching transistor 300 is electrically connected to a gateline 301. One of a source and a drain of the switching transistor 300 iselectrically connected to a source line 302. A first terminal of acapacitor 303 is electrically connected to the other of the source andthe drain of the switching transistor 300. A second terminal of thecapacitor 303 is electrically connected to a power supply line 304. Agate of a driving transistor 305 is electrically connected to the otherof the source and the drain of the switching transistor 300. One of asource and a drain of the driving transistor 305 is electricallyconnected to one of electrodes of a light-emitting element 306. Theother of the electrodes of the light-emitting element 306 iselectrically connected to a power supply line 307. The other of thesource and the drain of the driving transistor 305 is electricallyconnected to the power supply line 304. A first terminal of a switch 308is electrically connected to the power supply line 304. A secondterminal of the switch 308 is electrically connected to a column line309. A third terminal of the switch 308 is electrically connected to arow line 310. Although a p-channel transistor is illustrated as thedriving transistor 305 here, an n-channel transistor may be used.

FIG. 6 illustrates column lines (lines for detecting x coordinates) androw lines (lines for detecting y coordinates) for detecting a position(a touch position 351) where the touch panel is touched with a finger orthe like.

When the touch panel is touched with a finger or the like, the upperelectrode and the lower electrode are in contact with each other, sothat signals are input to detectors 350 which are connected to thecolumn line 309 and the row line 310. In the case where the detector isan ammeter, current flows through the detector. In the case where thedetector is a voltmeter, voltage is applied to the detector. In FIG. 5A,the x coordinates are detected by the column lines and the y coordinatesare detected by the row lines.

Note that this embodiment can be combined with the structure describedin any of the other embodiments in this specification as appropriate.

Embodiment 5

In this embodiment, the operation of a resistive type touch panel whichis different from that in Embodiment 4 is described.

FIG. 5B illustrates one embodiment of one pixel included in theresistive type touch panel. A top view of FIG. 5B is illustrated in FIG.14 or FIG. 24, for example.

The switching transistor 300, the gate line 301, the source line 302,the capacitor 303, the power supply line 304, the driving transistor305, the light-emitting element 306, and the power supply line 307 aresimilar to those in FIG. 5A. A first terminal of a switch 311 iselectrically connected to a column line 312. A second terminal of theswitch 311 is electrically connected to a power supply line 313.Although the upper electrode of the touch sensor is electricallyconnected to the power supply line 304 in FIG. 5A, the upper electrodeof the touch sensor is not electrically connected to the power supplyline 304 in FIG. 5B.

When the touch panel is touched with a finger or the like, the upperelectrode is in contact with the lower electrode, so that a signal isinput from the power supply line 313 to a detector which is connected tothe column line 312. It is necessary to decide a potential of the powersupply line 313 or the structure of the detector so that the xcoordinates and the y coordinates can be detected. Thus, a touchposition can be detected.

Note that this embodiment can be combined with the structure describedin any of the other embodiments in this specification as appropriate.

Embodiment 6

In this embodiment, a material used for the filler layer 112 illustratedin FIGS. 1A and 1B is described. As described in Embodiment 1, adeformable porous material or an elastic insulating material can be usedfor the filler layer 112.

As the deformable porous material, it is preferable to use a materialwhich is softened or hardened by certain treatment (e.g., heat treatmentor chemical treatment) after formation. As such a material, a blockcopolymer or a graft copolymer, which forms a microphase separationstructure, can be used, for example.

A block copolymer refers to a straight chain copolymer including aplurality of homopolymer chains as blocks linked together. For example,a diblock copolymer is given. Further, a block copolymer typified by atriblock copolymer, which includes three or more kinds of polymer chainslinked together, may be used.

A graft copolymer refers to a copolymer having a structure in whichother polymer chains as side chains are linked to the main chain of apolymer. The polymer chains linked as side chains may be of differentkinds.

Note that as the material used for the filler layer 112, a blockcopolymer is preferably used. This is because with the block copolymer,a polymer with a narrow molecular weight distribution can be obtainedeasily and a composition ratio can be controlled comparatively easily.By controlling the composition ratio of the material used for the fillerlayer 112, the volume occupied by a hole per unit volume of the fillerlayer 112 can be controlled. Thus, the amount of deformation in thefiller layer 112 for unit load can be varied. A block copolymer whichcan be applied to one embodiment of the present invention is describedbelow.

It is known that a block copolymer spontaneously forms a nanometer-scalemicrophase separation structure. For example, an AB block copolymer ismicrophase-separated to form a periodic structure such as a sphericalstructure, a cylinder structure, a gyroid structure, or a lamellastructure depending on the composition ratio of a high molecularcompound included in the block copolymer. Note that when the rate of oneof components is less than or equal to approximately 20%, a sphericalstructure is formed (see FIG. 7A or FIG. 7E); when the rate is greaterthan or equal to approximately 20% and less than or equal toapproximately 35%, a cylinder structure is formed (see FIG. 7B or FIG.7D); when the rate is greater than or equal to approximately 35% andless than or equal to approximately 40%, a gyroid structure is formed(see FIG. 7F or FIG. 7G); and when the rate is greater than or equal toapproximately 40%, a lamella structure is formed (see FIG. 7C). Notethat a chemical solution does not easily reach a surface of the fillerlayer in wet etching and one of the components which should be removedis difficult to remove in the case of a spherical structure. Thus, acylinder structure, a gyroid structure, or a lamella structure ispreferably employed.

For production of a block copolymer, living polymerization can be used,for example. The living polymerization refers to a method by whichpolymerization of one kind of monomer is initiated by a polymerizationinitiator which generates anions or cations and a different monomer issequentially added for synthesis, so that a block copolymer is produced.The production method is described below.

First, materials included in a block copolymer are dissolved in asolvent. This solvent is preferably a good solvent for all the pluralkinds of polymers included in the block copolymer. Here, the goodsolvent refers to a solvent which can produce a homogeneous solution ofthe polymers included in the block copolymer. Since two kinds ofpolymers are used here, a homogeneous solution of the two kinds ofpolymers may be produced. For example, a toluene solution of about 5% byweight of the block copolymer is applied to a region where the fillerlayer 112 is formed with a spin coating method or the like. Note thatalthough the solution is applied to the entire surface of a substrate bythe spin coating method, the solution is applied to only a desiredregion with the use of a droplet discharge method, for example. Thus, alater process is simplified and material use efficiency is improved.

Next, heat treatment is performed on the substrate to which the solutionis applied, and microphase separation is induced. Heat treatmenttemperature is set greater than or equal to the glass transition pointof the components included in the block copolymer and less than or equalto the phase transition temperature thereof.

Note that there are different kinds of block copolymers, typically, astyrene-butadiene AB block copolymer and a styrene-isoprene AB blockcopolymer. Besides, there are a block copolymer including differentmaterials, such as polymethylmethacrylate (PMMA); a block copolymerobtained by attaching a modified group to a terminal group of astyrene-isoprene block copolymer; and the like. Examples of a highmolecular segment of the block copolymer include hydrophobic aromatichydrocarbon chains such as polystyrene and polyfluorene, hydrophobicaliphatic unsaturation hydrocarbon chains such as polybutadiene andpolyisoprene, hydrophilic aliphatic hydrocarbon chains such as polyvinylalcohol and polyethylene glycol, hydrophilic aromatic hydrocarbon chainssuch as polystyrene sulfonic acid, hydrophobic siloxanes such aspolydimethylsiloxane, metal complexes such as polyferrocene, and thelike. Further, the block copolymer is linear, branched, or cyclic bycovalent bond of two or more kinds of these high molecular segments atone or more bonding points.

The above material may further contain a solvent. Examples of thesolvent include aliphatic hydrocarbons such as hexane, heptane, andoctane; halogenated hydrocarbons such as carbon tetrachloride,chloroform, and dichloromethane; aromatic hydrocarbons such as benzene,toluene, and xylene; ketones such as acetone and methyl ethyl ketone;ethers such as dimethyl ether and diethyl ether; alcohols such asmethanol and ethanol; water; and the like. The solvent can be selectedfrom these solvents depending on properties or conditions of a materialwhich is to be formed.

In this embodiment, the filler layer 112 can be formed and one of thecomponents of the block copolymer can be selectively etched away.Further, an ABA block copolymer or a BAB block copolymer can have any ofa variety of structures such as a spherical structure and a lamellastructure depending on the composition of the block copolymer. Note thatin the present invention, it is preferable to employ a cylinderstructure, a gyroid structure, or a lamella structure, as describedabove.

Note that in this embodiment, a material which can be used for thefiller layer 112 is not limited to the above materials and may be amaterial formed using plural kinds of substances, in which one kind ofthe substances can be removed by etching or the like in a later step.Further, although the substance removed by etching or the like is notnecessarily one kind of the substances, it is necessary at the veryleast that at least one kind of the substances in the filler layer 112be not removed after one kind of the substances is removed by etching orthe like. Furthermore, heat resistance and chemical resistance areneeded such that the material can withstand a process after theformation of the filler layer 112. Here, the substance remaining in thefiller layer 112 without being removed is preferably a substance whichis capable of elastic deformation.

Note that in this embodiment, the filler layer 112 can be formed using ablock copolymer as described above. In the case where the filler layer112 is formed using a block copolymer, porosity can be higher than orequal to approximately 20% and lower than or equal to 80% by making thevolume of one of materials used for the filler layer 112 higher than orequal to 20% and lower than or equal to 80%. Thus, formation of thefiller layer 112 itself or formation of the holes in the filler layer112 can be performed favorably. The porosity is preferably higher thanor equal to 20% and less than or equal to 60%. By making the porosityhigher than or equal to 20% and less than or equal to 60%, the fillerlayer 112 has a cylinder structure, a gyroid structure, or a lamellastructure. By making the porosity higher than or equal to 20% and lessthan or equal to 60%, the volume of the holes is less than the volume ofthe material used for the filler layer 112 even in the case where thefiller layer 112 has a cylinder structure or a gyroid structure. Thus,the filler layer 112 is dense, so that sufficient mechanical strengthcan be secured. Still preferably, the porosity is higher than or equalto 20% and less than or equal to 35%. By making the porosity higher thanor equal to 20% and less than or equal to 35%, the volume of thematerial used for the filler layer 112 is increased, so that the fillerlayer 112 has a cylinder structure having sufficient mechanicalstrength.

As described above, the filler layer 112 can be formed using adeformable porous material. However, this embodiment is not limited tothis. For example, the filler layer 112 may be formed using an elasticinsulating material. The case where the filler layer 112 is formed usingan elastic insulating material is described below.

As the elastic insulating material, it is preferable to use a materialwhich is softened or hardened by certain treatment (e.g., heat treatmentor chemical treatment) after formation. As such a material, an elastomeror a thermoplastic elastomer can be used, for example. Formation can beeasily performed when an elastomer or a thermoplastic elastomer is used,which is preferable.

Note that an elastomer refers to an organic resin material which hasflexibility and impact resilience and has a Young's modulus ofapproximately 1.0×10⁶ Pa to 1.0×10⁷ Pa. An antonym of an elastomer is aplastomer.

As the material used for the filler layer 112, a polymer elastomer ispreferably used. As the polymer elastomer, a polyurethane resin, anethylene-vinyl acetate resin, an ethylene-ethyl acrylate resin, apolyester resin, a polyamide resin, synthetic rubber such as butadienerubber, butyl rubber, styrene-butadiene rubber, nitrile rubber, isoprenerubber, chloroprene rubber, or silicone rubber, or a deformed materialthereof can be used; however, this embodiment is not limited to this.One or more kinds of the above materials may be used. Alternatively,elastic modulus may be adjusted by addition of a plasticizer or thelike.

As a formation method of the polymer elastomer, a dipping method, acoating method, a screen printing method, a gravure printing method, aspray coating method, a droplet discharge method, or the like may beused, for example. In the case where the polymer elastomer is formedusing such a method, it is necessary to solidify the elastomer after asolution containing the material used for the polymer elastomer as asolute is formed. Therefore, the polymer elastomer used for the fillerlayer 112 is preferably an elastomer which is dried at normaltemperature or a normal-temperature cross-linked elastomer. When anelastomer which is dried at normal temperature or a normal-temperaturecross-linked elastomer is used, treatment for solidifying the elastomer(e.g., heat treatment or drying treatment) is not needed, so that amanufacturing process is simplified.

Note that the elastomer which is dried at normal temperature or thenormal-temperature cross-linked elastomer refers not only to anelastomer which is dried at normal temperature or an elastomer whichforms a cross link at normal temperature but also to an elastomer whichis dried at a temperature slightly higher than normal temperature or anelastomer which forms a cross link at a temperature slightly higher thannormal temperature. In addition, as a solvent in the elastomer dried atnormal temperature, it is preferable to use a solvent whose boilingtemperature is slightly higher than normal temperature rather than asolvent whose boiling temperature is substantially the same as normaltemperature. This is because boiling might occur at the time offormation when a solvent whose boiling temperature is substantially thesame as normal temperature is used. For example, it is preferable to usebenzene (whose boiling temperature is 80° C.) or chloroform (whoseboiling temperature is 61° C.) rather than methylene chloride (whoseboiling temperature is 40° C.) or acetone (whose boiling temperature is56° C.). Further, any of the solvents which might evaporate after beingleft for a certain period of time can be used.

Note that the normal temperature generally refers to a temperature rangefrom 15 to 25° C.; however, the present invention is not limited tothis. As the elastomer which is dried at normal temperature or thenormal-temperature cross-linked elastomer, an elastomer which is driedat approximately 0 to 100° C. or an elastomer which forms a cross linkat approximately 0 to 100° C. may be used. It is needless to say thatdrying or the formation of a cross link is preferably performed at lowtemperature within the above temperature range.

As the formation method of the elastomer or the thermoplastic elastomerused for the filler layer 112, a spin coating method is most preferablyused. This is because the filler layer 112 can be formed withoutgeneration of unevenness in the thickness and quality of the fillerlayer 112 with the use of a spin coating method. By making uniformity inthe thickness and quality of the filler layer 112 higher, generation ofunevenness in strength distribution of the filler layer 112 can beprevented. Thus, yield and reliability are improved, which ispreferable.

The elastomer which is dried at normal temperature can be formed bydissolution of a solid body of a polymer elastomer into an organicsolvent which volatilizes at normal temperature. For example,solvent-diluting urethane, solvent-diluting acrylic, or the like may beused.

As the normal-temperature cross-linked elastomer, a moisture-curableelastomer which is cured by absorption of moisture contained in the airor an elastomer which is cured with energy such as an ultraviolet (UV)ray, an electron beam (EB), or visible light (an UV curable elastomer,an EB curable elastomer, or a visible light curable elastomer) may beused. In the case where a visible light curable elastomer is used, it isacceptable that certain processing is performed in a space which isshielded from visible light and exposure to visible light is performedonly when the elastomer is cured. By using the visible light curableelastomer, the filler layer 112 can be formed while a layer which hasbeen formed is not irradiated with an ultraviolet ray, an electron beam,or the like. Thus, an apparatus for irradiation with an ultraviolet ray,an electron beam, or the like is not needed, which is preferable. Thevisible light curable elastomer can be formed in such a manner that anelastomer is dissolved in an organic solvent or the like or an elastomeris dispersed into water. Alternatively, the visible light curableelastomer can be formed without the use of a medium such as a solvent.

In the case where the solid body of the polymer elastomer is dispersedinto water to be applied, it is difficult to form the elastomeruniformly. This is because solid ink includes many hydrophobiccomponents. Thus, it is preferable to form the elastomer without beingdispersed into water. As the normal-temperature cross-linked elastomer,a moisture-curable urethane resin, an UV curable acrylic resin, or thelike can be used, for example. The elastomer which is dried at normaltemperature and the normal-temperature cross-linked elastomer can beformed at not so high temperature, so that the filler layer 112 can beformed without transformation or the like of the layer which has beenformed.

In addition, since it is difficult to process an elastomer into adesired shape, a thermoplastic elastomer may be used. The use of athermoplastic elastomer is preferable because shaping is facilitated.That is, the use of a thermoplastic elastomer is preferable becauseprocessing into a variety of shapes or processing with high accuracy isfacilitated.

Note that the thermoplastic elastomer refers to an elastomer which hasflexibility, impact resilience, and the like at normal temperature andexhibits plasticity by heating. As the thermoplastic elastomer, aurethane type, a styrene type, a vinyl type, an ester type, and the likeare used; however, the material of the thermoplastic elastomer is notlimited to a certain material. Alternatively, a material which exhibitsplasticity with certain treatment may be used.

Note that in the case where a porous material is used for the fillerlayer 112, it is necessary to etch away any of the materials included ina block copolymer. A step of etching away any of the materials includedin the block copolymer is described below.

In order to remove one of components of the block copolymer, dry etchingor wet etching can be used. For example, reactive ion etching (RIE) inan oxygen gas atmosphere can be used. It is preferable to employ acondition that etching rates of a component which should be removed anda component which should remain in the block copolymer are greatlydifferent from each other. In general, the higher the content of carbonmolecules per unit molecule contained in a polymer molecular chain is,the higher etching resistance is; the higher the content of oxygenmolecules per segment is, the lower etching resistance is. For example,since polystyrene (PS) contains an aromatic ring, the content of carbonmolecules in a block copolymer of polystyrene-polymethylmethacrylate(PS-PMMA) is high. Thus, the etching resistance of the block copolymeris high. The etching resistance of polyacrylamide (PAAM) is low becausethe content of oxygen molecules is high. In the case of employing RIB,the etching rate of one of these two kinds of components is generallyfour times that of the other.

Note that a gas used for the etching is not limited to an oxygen gas andmay be CF₄, H₂, C₂F₆, CHF₃, CH₂F₂, CF₃Br, NF₃, Cl₂, CCl₄, HBr, SF₆ orthe like.

Note that the etching rate is determined per monomer unit of a blockcopolymer. It is known that when N denotes the total number of atoms permonomer unit, Nc denotes the number of carbon atoms per monomer unit,and No denotes the number of oxygen atoms per monomer unit, the etchingrate is proportional to N/(Nc−No).

However, in the above dry etching, although there is no problem in thecase of a cylinder structure or the like, many portions could fail to beetched in the case of a spherical structure. Thus, in the case of aspherical structure, wet etching is preferably used. Through wetetching, one of the components can be etched depending on the materialused for the formed block copolymer and the other of the components maybe etched under a condition of high etching resistance. However, inconsideration of the above circumstances, it is still preferable toemploy a cylinder structure, a gyroid structure, or a lamella structure.

Further, a method for removing the component which should be removed isnot necessarily limited to etching. If possible, the component whichshould be removed may be removed with evaporation, sublimation, or thelike by heat treatment or the like.

In the case where a block copolymer is used, the formation of the fillerlayer 112 is completed through the above steps.

Note that in FIGS. 1A and 1B, the filler layer 112 is formed in such amanner that an opening formed in the insulating layer 111 is filled withthe material used for the filler layer 112. Alternatively, after thematerial used for the filler layer 112 is formed over the insulatinglayer 111, the material used for the filler layer 112 is processed intoa desired shape to form the filler layer 112.

In the microstructure according to one embodiment of the presentinvention, unlike a conventional microstructure, a deformable materialis filled between the upper electrode and the lower electrode. Thus, amicrostructure having mechanical strength higher than a conventionalmicrostructure including a hollow portion can be formed. Improvement inmechanical strength makes it possible to prevent generation of a defectin a manufacturing process or operation. Thus, yield and reliability areimproved.

Note that this embodiment can be combined with the structure describedin any of the other embodiments in this specification as appropriate.

Embodiment 7

In this embodiment, structures of a touch panel which is one embodimentof the present invention are described with reference to FIG. 8, FIG. 9,FIG. 10, FIG. 11, FIG. 12, FIGS. 15A to 15C, FIG. 16, and FIG. 17. FIG.8, FIG. 9, FIG. 10, FIG. 11, and FIG. 12 are top views of one pixel ofthe touch panel which is one embodiment of the present invention. FIGS.15A to 15C, FIG. 16, and FIG. 17 are cross-sectional views taken alongline A-B in FIG. 12. Note that for simplicity, FIG. 8, FIG. 9, FIG. 10,FIG. 11, and FIG. 12 illustrate gate electrodes 402 and 403, a wiring404, a lower electrode 405, a row line (a line for detecting a ycoordinate) 450, first semiconductor layers 407 and 408, conductivelayers 413, 414, 415, and 416, a column line (a line for detecting an xcoordinate) 451, a filler layer 419, a first electrode 420, a wiring421, and an upper electrode 422. Further, the touch panel described inthis embodiment is a touch panel which includes the capacitive typetouch sensor described in Embodiment 2 or the resistive type touchsensor described in Embodiment 4.

A base film 401 is formed over a substrate 400 (see FIG. 15A). As thesubstrate 400, a plastic substrate having heat resistance enough towithstand the processing temperature of a transistor, or the like aswell as a glass substrate formed with a fusion method or a float method,such as a barium borosilicate glass substrate, an aluminoborosilicateglass substrate, or an aluminosilicate glass substrate, a ceramicsubstrate can be used. Alternatively, a metal substrate such as astainless steel alloy substrate which is provided with an insulatingfilm over a surface may be used.

The base film 401 is formed using a single-layer structure or a layeredstructure of an insulating film such as a silicon oxide-based materialfilm or a silicon nitride-based material. Note that the siliconoxide-based material refers to silicon oxide containing oxygen andsilicon as main components, or silicon oxynitride which is silicon oxidecontaining nitrogen, in which the content of oxygen is higher than thatof nitrogen. The silicon nitride-based material refers to siliconnitride containing nitrogen and silicon as main components, or siliconnitride oxide which is silicon nitride containing oxygen, in which thecontent of nitrogen is higher than that of oxygen.

A transistor is formed over the base film 401. The transistor may haveany shape and may be formed with any method. In this embodiment, abottom-gate (inverted-staggered) transistor, particularly, achannel-etched transistor is described.

The gate electrodes 402 and 403, the wiring 404, and the lower electrode405 of a microstructure (MEMS) are formed over the base film 401 (seeFIG. 8 and FIG. 15A). After a conductive film is formed over the basefilm 401, the conductive film is etched as in FIG. 8. Thus, the gateelectrodes 402 and 403, the wiring 404, and the lower electrode 405 areformed using the same material. The gate electrodes 402 and 403, thewiring 404, and the lower electrode 405 can be formed using a conductivemetal or a semiconductor material, such as titanium, molybdenum,tantalum, chromium, tungsten, aluminum, neodymium, copper, silver, gold,platinum, niobium, silicon, zinc, iron, barium, or germanium; or analloy material thereof with sputtering, CVD, or the like. Alternatively,the gate electrodes 402 and 403, the wiring 404, and the lower electrode405 may be formed by stacking two or more kinds of conductive materials.Further, side surfaces of the gate electrodes 402 and 403 may be etchedto be tapered. Note that in FIG. 8, reference numeral 450 denotes a rowline (a line for detecting a y coordinate). The row line 450 is formedusing the same material as the gate electrodes 402 and 403, the wiring404, and the lower electrode 405.

An insulating film 406 is formed over the gate electrodes 402 and 403,the wiring 404, and the lower electrode 405 (see FIG. 15A). Theinsulating film 406 can be formed using a silicon oxide-based material,a silicon nitride-based material, or the like with plasma-enhanced CVD,sputtering, or the like. Alternatively, the insulating film 406 can beformed by high-density plasma treatment. Here, high-density plasmatreatment refers to plasma treatment where plasma density is higher thanor equal to 1×10¹¹ cm⁻³, preferably, higher than or equal to 1×10¹¹ cm⁻³and lower than or equal to 9×10¹⁵ cm⁻³ and a high-frequency wave such asa microwave (e.g., a frequency of 2.45 GHz) is used. When plasma isgenerated under such a condition, low electron temperature is higherthan or equal to 0.2 eV and lower than or equal to 2.0 eV. Since suchhigh-density plasma at low electron temperature has low kinetic energyof active species, it is possible to form a film with little plasmadamage and fewer defects. In the insulating film formed by thehigh-density plasma treatment in this manner, the state of an interfacebetween the insulating film and a layer which is in contact with theinsulating film is improved. Thus, when the insulating film 406 isformed by high-density plasma treatment, the state of an interfacebetween the insulating film 406 and the semiconductor layer can beimproved. Accordingly, electrical properties of a semiconductor elementcan be improved.

The first semiconductor layers 407 and 408 are formed over theinsulating film 406 (see FIG. 9 and FIG. 15A). The first semiconductorlayer 407 is formed so as to overlap with the gate electrode 402 withthe insulating film 406 therebetween. The first semiconductor layer 408is formed so as to overlap with the gate electrode 403 with theinsulating film 406 therebetween. The first semiconductor layers 407 and408 can be formed using a non-crystalline semiconductor layer formedusing amorphous silicon (a-Si:H) or the like, microcrystalline silicon(μ-Si:H), polycrystalline silicon, single crystal silicon, a compoundsemiconductor such as gallium arsenide (GaAs), or an oxide semiconductorsuch as zinc oxide (ZnO) or an In—Ga—Zn—O-based oxide semiconductor withphotolithography, an ink-jet method, a printing method, or the like.Note that the first semiconductor layers 407 and 408 have portionsfunctioning as channel regions of the transistors.

In the case where amorphous silicon (a-Si:H) or microcrystalline siliconis used for the first semiconductor layers 407 and 408, there areadvantages that the characteristics of the transistors are uniform andthat manufacturing cost is low. In particular, the use of amorphoussilicon (a-Si:H) or microcrystalline silicon is effective in formingtransistors over a large substrate whose diagonal length exceeds 500 mm.

In the case where polycrystalline silicon is used for the firstsemiconductor layers 407 and 408, there are advantages that thetransistors have high mobility and that manufacturing cost is low.Further, since deterioration in characteristics over time is little, ahighly reliable device can be obtained.

In the case where an oxide semiconductor is used for the firstsemiconductor layers 407 and 408, field effect mobility can be higherthan that of a thin film transistor including amorphous silicon. Anoxide semiconductor film can be formed with sputtering or the like at atemperature of 300° C. or lower, and a manufacturing process thereof issimpler than that of a thin film transistor including polycrystallinesilicon.

Note that as an example of an oxide semiconductor which can be used inthis specification, there is an oxide semiconductor represented byInMO₃(ZnO)_(m) (m>0). Here, M is one or more metal elements selectedfrom gallium (Ga), iron (Fe), nickel (Ni), manganese (Mn), or cobalt(Co). For example, the case where Ga is selected as M includes not onlythe case where only Ga is used but also the case where Ga and the abovemetal element other than Ga, such as Ni or Fe, are selected. Further, inthe oxide semiconductor, in some cases, a transitional metal elementsuch as Fe or Ni or an oxide of the transitional metal is contained asan impurity element in addition to the metal element contained as M. Inthis specification, among the oxide semiconductors, an oxidesemiconductor containing at least gallium as M is referred to as anIn—Ga—Zn—O-based oxide semiconductor, and a thin film formed using thematerial is referred to as an In—Ga—Zn—O-based non-single-crystal filmin some cases.

Second semiconductor layers 409 and 410 are formed over the firstsemiconductor layer 407, and second semiconductor layers 411 and 412 areformed over the first semiconductor layer 408 (see FIG. 15A). The secondsemiconductor layer 409 has a portion functioning as one of a source anda drain. The second semiconductor layer 410 has a portion functioning asthe other of the source and the drain. The second semiconductor layer411 has a portion functioning as one of a source and a drain. The secondsemiconductor layer 412 has a portion functioning as the other of thesource and the drain. Note that for the second semiconductor layers,silicon containing phosphorus or the like, a semiconductor materialhaving higher conductivity than the first semiconductor layer, an oxidesemiconductor having higher carrier concentration than the firstsemiconductor layer, or the like can be used. The second semiconductorlayers can be each referred to as a buffer layer or an n⁺ layerdepending on its function.

The conductive layers 413, 414, 415, and 416 are formed over the secondsemiconductor layers 409, 410, 411, and 412 (see FIG. 10 and FIG. 15B).The conductive layer 413 has a portion functioning as one of a sourceand a drain. The conductive layer 414 has a portion functioning as theother of the source and the drain. The conductive layer 415 has aportion functioning as one of a source and a drain. The conductive layer416 has a portion functioning as the other of the source and the drain.The conductive layers 413, 414, 415, and 416 can be formed using aconductive metal or a semiconductor material, such as titanium,molybdenum, tantalum, chromium, tungsten, aluminum, neodymium, copper,silver, gold, platinum, niobium, silicon, zinc, iron, barium, orgermanium; or an alloy material thereof with sputtering, CVD, or thelike. Note that in FIG. 10, reference numeral 451 denotes a column line(a line for detecting an x coordinate). The column line 451 is formedusing the same material as the conductive layers 413, 414, 415, and 416.

A passivation film 417 is formed over the conductive layers 413, 414,415, and 416 (see FIG. 15B). An insulating film formed using siliconnitride or the like can be used as the passivation film 417.

An insulating layer 418 is formed over the passivation film 417 (seeFIG. 15B). The insulating layer 418 is formed using a siliconoxide-based material film or a silicon nitride-based material film. Inaddition, for the insulating layer 418, an organic resin such aspolyimide, polyamide, acrylic (including photosensitive acrylic), orbenzocyclobutene (BCB) can be used. Further, the insulating layer 418may have either a single-layer structure or a layered structure.

By etching the insulating layer 418, part of the conductive layer 414and part of the lower electrode 405 are exposed so that contact holesare formed. Next, the filler layer 419 is formed so as to fill thecontact hole formed (see FIG. 11 and FIG. 15B). A deformable porousmaterial or an elastic insulating material can be used for the fillerlayer 419, and any of the materials described in Embodiment 6 can beused.

Note that the filler layer 419 is formed in such a manner that thecontact hole formed in the insulating layer 418 is filled with thematerial used for the filler layer 419. Alternatively, after thematerial used for the filler layer 419 is formed over the insulatinglayer 418, the material used for the filler layer 419 is processed intoa desired shape to form the filler layer 419.

A conductive layer is formed over the insulating layer 418 and thefiller layer 419 and is etched to have a desired shape, so that thefirst electrode 420, the wiring 421, and the upper electrode 422 of themicrostructure (MEMS) are formed (see FIG. 12 and FIG. 15C). The upperelectrode 422 is formed so as to overlap with the lower electrode 405with the filler layer 419 therebetween. The first electrode 420, thewiring 421, and the upper electrode 422 can be formed using a conductivemetal or a semiconductor material, such as titanium, molybdenum,tantalum, chromium, tungsten, aluminum, neodymium, copper, silver, gold,platinum, niobium, silicon, zinc, iron, barium, or germanium; or analloy material thereof with sputtering, CVD, or the like.

A partition wall 423 which covers an end portion of the first electrode420 and has an opening reaching the upper electrode 422 is formed (seeFIG. 15C). For the partition wall 423, an organic resin film, aninorganic resin film, or an organic polysiloxane can be used.Specifically, the partition wall 423 is preferably formed usingpolyimide, polyamide, polyimide amide, acrylic, or abenzocyclobutene-based resin. It is particularly preferable that thepartition wall 423 be formed using a photosensitive material to have anopening over the first electrode 420 and the upper electrode 422 so thata sidewall of the opening is formed as a tilted surface with continuouscurvature.

A spacer 424 is formed so as to fill the opening in the partition wall423 reaching the upper electrode 422 (see FIG. 15C). An ultravioletcurable resin or the like can be used for the spacer 424. Specifically,the spacer 424 may be formed using an ultraviolet curable acrylic resinor the like. Note that the spacer 424 is formed so as to overlap withthe lower electrode 405.

Here, among the materials used for the filler layer 419, the partitionwall 423, and the spacer 424, the material used for the spacer 424 isthe hardest material and the material used for the filler layer 419 isthe softest material. Elastic modulus or the like indicates hardness orsoftness. The elastic modulus is a physical value indicating an object'stendency to be deformed elastically. In the case where hardness orsoftness is indicated by elastic modulus, the elastic modulus of thematerial used for the spacer 424 is higher than the elastic modulus ofthe material used for the partition wall 423, and the elastic modulus ofthe material used for the partition wall 423 is higher than the elasticmodulus of the material used for the filler layer 419.

An EL layer 425 is formed over the first electrode 420 (see FIG. 15C).The EL layer 425 includes a hole injection layer, a hole transportlayer, a light-emitting layer, an electron transport layer, an electroninjection layer, a hole blocking layer, and the like. The material usedfor the EL layer 425 may be selected as appropriate.

A second electrode 426 is formed over the EL layer 425 and the partitionwall 423 (see FIG. 15C). The first electrode 420, the EL layer 425, andthe second electrode 426 are included in a light-emitting element. Thesecond electrode 426 can be formed using a light-transmitting conductivematerial. As the light-transmitting conductive material, indium tinoxide (hereinafter referred to as ITO), indium oxide containing tungstenoxide, indium zinc oxide containing tungsten oxide, indium oxidecontaining titanium oxide, indium tin oxide containing titanium oxide,indium zinc oxide, indium tin oxide to which silicon oxide is added, orthe like can be used. The film formed using the light-transmittingconductive material may be formed with sputtering, CVD, or the like;however, this embodiment is not limited to a particular method. Further,the second electrode 426 may have either a single-layer structure or alayered structure.

Through the above steps, an element substrate can be formed. Then,sealing is performed in such a manner that a sealant (not illustrated)is provided at an end portion of the element substrate and the elementsubstrate and a sealing substrate 427 are attached to each other withthe sealant (see FIG. 16). The touch panel which is one embodiment ofthe present invention has a structure where a light-emitting element isprovided in a space 428 surrounded by the element substrate, the sealingsubstrate 427, and the sealant. The space 428 is filled with an inertgas (e.g., nitrogen or argon). The space 428 may be filled with asealant as a substitute for the inert gas.

Note that an epoxy-based resin is preferably used for the sealant. Inaddition, it is preferable to use a material which does not transmitmoisture or oxygen as much as possible. Further, as the sealingsubstrate 427, a glass substrate, a plastic substrate formed usingfiberglass-reinforced plastics (FRP), polyvinyl fluoride (PVF),polyester, acrylic, or the like can be used.

Next, FIG. 17 illustrates the case where the touch panel is touched witha finger.

As illustrated in FIG. 17, when the sealing substrate 427 is touchedwith a finger 429, the sealing substrate 427 bends. In this case, anupper portion of the partition wall 423 is pressed and dented, and thespacer 424 which is harder (which has higher elastic modulus) than thematerial used for the partition wall 423 is pressed down. Since thefiller layer 419 provided below the spacer 424 is softer (has lowerelastic modulus) than the spacer 424, the spacer 424 is pressed downwithout deformation. The upper electrode 422 of the microstructure(MEMS) is pressed down when the spacer 424 is pressed down. In the caseof the capacitive type touch panel, the distance between the lowerelectrode 405 and the upper electrode 422 of the microstructure (MEMS)is changed. Thus, data can be input. In the case of the resistive typetouch panel, the lower electrode 405 and the upper electrode 422 of themicrostructure (MEMS) are in contact with each other. Thus, data can beinput.

According to one embodiment of the present invention, a touch sensor canbe formed in steps of forming a thin film transistor and alight-emitting element.

According to one embodiment of the present invention, a touch sensor anda light-emitting element are disposed, so that it is possible to providea thin touch panel with less degradation in image quality as compared tothe case where a touch sensor is provided above or below alight-emitting element.

According to one embodiment of the present invention, by using materialshaving different hardness for a filler layer, a partition wall, and aspacer, it is possible to provide a touch panel where data can be inputefficiently and pressure is not applied to a light-emitting elementeasily. Further, by providing a spacer above a touch sensor, durabilityand sensitivity of the touch sensor can be improved.

Note that this embodiment can be combined with the structure describedin any of the other embodiments in this specification as appropriate.

Embodiment 8

In this embodiment, structures of a touch panel which is different fromthat in Embodiment 7 are described with reference to FIG. 18, FIG. 19,FIG. 20, FIG. 21, FIG. 22, FIGS. 25A to 25C, FIG. 26, and FIG. 27. FIG.18, FIG. 19, FIG. 20, FIG. 21, and FIG. 22 are top views of one pixel ofthe touch panel which is one embodiment of the present invention. FIGS.25A to 25C, FIG. 26, and FIG. 27 are cross-sectional views taken alongline C-D in FIG. 22. Note that for simplicity, FIG. 18, FIG. 19, FIG.20, FIG. 21, and FIG. 22 illustrate gate electrodes 502 and 503, awiring 504, a row line (a line for detecting a y coordinate) 550, firstsemiconductor layers 506 and 507, conductive layers 512, 513, 514, and515, a lower electrode 516, a column line (a line for detecting an xcoordinate) 551, a filler layer 519, a first electrode 520, a wiring521, and an upper electrode 522. Further, the touch panel described inthis embodiment is a touch panel which includes the capacitive typetouch sensor described in Embodiment 2 or the resistive type touchsensor described in Embodiment 4.

A base film 501 is formed over a substrate 500 (see FIG. 25A). As thesubstrate 500, a plastic substrate having heat resistance enough towithstand the processing temperature of a transistor, or the like aswell as a glass substrate formed with a fusion method or a float method,such as a barium borosilicate glass substrate, an aluminoborosilicateglass substrate, or an aluminosilicate glass substrate, a ceramicsubstrate can be used. Alternatively, a metal substrate such as astainless steel alloy substrate which is provided with an insulatingfilm over a surface may be used.

The base film 501 is formed using a single-layer structure or a layeredstructure of an insulating film such as a silicon oxide-based materialfilm or a silicon nitride-based material. Note that the siliconoxide-based material refers to silicon oxide containing oxygen andsilicon as main components, or silicon oxynitride which is silicon oxidecontaining nitrogen, in which the content of oxygen is higher than thatof nitrogen. The silicon nitride-based material refers to siliconnitride containing nitrogen and silicon as main components, or siliconnitride oxide which is silicon nitride containing oxygen, in which thecontent of nitrogen is higher than that of oxygen.

A transistor is formed over the base film 501. The transistor may haveany shape and may be formed with any method. In this embodiment, abottom-gate (inverted-staggered) transistor, particularly, achannel-etched transistor is described.

The gate electrodes 502 and 503 and the wiring 504 are formed over thebase film 501 (see FIG. 25A). After a conductive film is formed over thebase film 501, the conductive film is etched as in FIG. 18. The gateelectrodes 502 and 503 and the wiring 504 can be formed using aconductive metal or a semiconductor material, such as titanium,molybdenum, tantalum, chromium, tungsten, aluminum, neodymium, copper,silver, gold, platinum, niobium, silicon, zinc, iron, barium, orgermanium; or an alloy material thereof with sputtering, CVD, or thelike. Alternatively, the gate electrodes 502 and 503 and the wiring 504may be formed by stacking two or more kinds of conductive materials.Further, side surfaces of the gate electrodes 502 and 503 may be etchedto be tapered. Note that in FIG. 18, reference numeral 550 denotes a rowline (a line for detecting a y coordinate). The row line 550 is formedusing the same material as the gate electrodes 502 and 503 and thewiring 504.

An insulating film 505 is formed over the gate electrodes 502 and 503and the wiring 504 (see FIG. 25A). The insulating film 505 can be formedusing a silicon oxide-based material, a silicon nitride-based material,or the like with plasma-enhanced CVD, sputtering, or the like.Alternatively, the insulating film 505 can be formed by high-densityplasma treatment. Here, high-density plasma treatment refers to plasmatreatment where plasma density is higher than or equal to 1×10¹¹ cm⁻³,preferably, higher than or equal to 1×10¹¹ cm⁻³ and lower than or equalto 9×10¹⁵ cm⁻³ and a high-frequency wave such as a microwave (e.g., afrequency of 2.45 GHz) is used. When plasma is generated under such acondition, low electron temperature is higher than or equal to 0.2 eVand lower than or equal to 2.0 eV. Since such high-density plasma at lowelectron temperature has low kinetic energy of active species, it ispossible to form a film with little plasma damage and fewer defects. Inthe insulating film formed by the high-density plasma treatment in thismanner, the state of an interface between the insulating film and alayer which is in contact with the insulating film is improved. Thus,when the insulating film 505 is formed by high-density plasma treatment,the state of an interface between the insulating film 505 and thesemiconductor layer can be improved. Accordingly, electrical propertiesof a semiconductor element can be improved.

The first semiconductor layers 506 and 507 are formed over theinsulating film 505 (see FIG. 19 and FIG. 25A). The first semiconductorlayer 506 is formed so as to overlap with the gate electrode 502 withthe insulating film 505 therebetween. The first semiconductor layer 507is formed so as to overlap with the gate electrode 503 with theinsulating film 505 therebetween. The first semiconductor layers 506 and507 can be formed using a non-crystalline semiconductor layer formedusing amorphous silicon (a-Si:H) or the like, microcrystalline silicon(μ-Si:H), polycrystalline silicon, single crystal silicon, a compoundsemiconductor such as gallium arsenide (GaAs), or an oxide semiconductorsuch as zinc oxide (ZnO) or an In—Ga—Zn—O-based oxide semiconductor withphotolithography, an ink-jet method, a printing method, or the like.Note that the first semiconductor layers 506 and 507 have portionsfunctioning as channel regions of the transistors.

In the case where amorphous silicon (a-Si:H) or microcrystalline siliconis used for the first semiconductor layers 506 and 507, there areadvantages that the characteristics of the transistors are uniform andthat manufacturing cost is low. In particular, the use of amorphoussilicon (a-Si:H) or microcrystalline silicon is effective in formingtransistors over a large substrate whose diagonal length exceeds 500 mm.

In the case where polycrystalline silicon is used for the firstsemiconductor layers 506 and 507, there are advantages that thetransistors have high mobility and that manufacturing cost is low.Further, since deterioration in characteristics over time is little, ahighly reliable device can be obtained.

In the case where an oxide semiconductor is used for the firstsemiconductor layers 506 and 507, field effect mobility can be higherthan that of a thin film transistor including amorphous silicon. Anoxide semiconductor film can be formed with sputtering or the like at atemperature of 300° C. or lower, and a manufacturing process thereof issimpler than that of a thin film transistor including polycrystallinesilicon.

Note that as an example of an oxide semiconductor which can be used inthis specification, there is an oxide semiconductor represented byInMO₃(ZnO)_(m) (m>0). Here, M is one or more metal elements selectedfrom gallium (Ga), iron (Fe), nickel (Ni), manganese (Mn), or cobalt(Co). For example, the case where Ga is selected as M includes not onlythe case where only Ga is used but also the case where Ga and the abovemetal element other than Ga, such as Ni or Fe, are selected. Further, inthe oxide semiconductor, in some cases, a transitional metal elementsuch as Fe or Ni or an oxide of the transitional metal is contained asan impurity element in addition to the metal element contained as M. Inthis specification, among the oxide semiconductors, an oxidesemiconductor containing at least gallium as M is referred to as anIn—Ga—Zn—O-based oxide semiconductor, and a thin film formed using thematerial is referred to as an In—Ga—Zn—O-based non-single-crystal filmin some cases.

Second semiconductor layers 508 and 509 are formed over the firstsemiconductor layer 506, and second semiconductor layers 510 and 511 areformed over the first semiconductor layer 507 (see FIG. 25A). The secondsemiconductor layer 508 has a portion functioning as one of a source anda drain. The second semiconductor layer 509 has a portion functioning asthe other of the source and the drain. The second semiconductor layer510 has a portion functioning as one of a source and a drain. The secondsemiconductor layer 511 has a portion functioning as the other of thesource and the drain. Note that for the second semiconductor layers,silicon containing phosphorus or the like, a semiconductor materialhaving higher conductivity than the first semiconductor layer, an oxidesemiconductor having higher carrier concentration than the firstsemiconductor layer, or the like can be used. The second semiconductorlayers can be each referred to as a buffer layer or an n⁺ layerdepending on its function.

The conductive layers 512, 513, 514, and 515 and the lower electrode 516of a microstructure (MEMS) are formed over the insulating film 505 andthe second semiconductor layers 508, 509, 510, and 511 (see FIG. 20 andFIG. 25B). The conductive layer 512 has a portion functioning as one ofa source and a drain. The conductive layer 513 has a portion functioningas the other of the source and the drain. The conductive layer 514 has aportion functioning as one of a source and a drain. The conductive layer515 has a portion functioning as the other of the source and the drain.The conductive layers 512, 513, 514, and 515 and the lower electrode 516can be formed using a conductive metal or a semiconductor material, suchas titanium, molybdenum, tantalum, chromium, tungsten, aluminum,neodymium, copper, silver, gold, platinum, niobium, silicon, zinc, iron,barium, or germanium; or an alloy material thereof with sputtering, CVD,or the like. Note that in FIG. 20, reference numeral 551 denotes acolumn line (a line for detecting an x coordinate). The column line 551is formed using the same material as the conductive layers 512, 513,514, and 515 and the lower electrode 516.

A passivation film 517 is formed over the conductive layers 512, 513,514, and 515 and the lower electrode 516 (see FIG. 25B). Silicon nitrideor the like can be used for the passivation film 517.

An insulating layer 518 is formed over the passivation film 517 (seeFIG. 25B). The insulating layer 518 is formed using a siliconoxide-based material film or a silicon nitride-based material film. Inaddition, for the insulating layer 518, an organic resin such aspolyimide, polyamide, acrylic (including photosensitive acrylic), orbenzocyclobutene (BCB) can be used. Further, the insulating layer 518may have either a single-layer structure or a layered structure.

By etching the insulating layer 518, the conductive layer 513 and thelower electrode 516 are exposed so that contact holes are formed. Next,the filler layer 519 is formed so as to fill the contact hole formed(see FIG. 21 and FIG. 25B). A deformable porous material or an elasticinsulating material can be used for the filler layer 519, and any of thematerials described in Embodiment 6 can be used.

A conductive layer is formed over the insulating layer 518 and thefiller layer 519 and is etched to have a desired shape, so that thefirst electrode 520, the wiring 521, and the upper electrode 522 of themicrostructure (MEMS) are formed (see FIG. 22 and FIG. 25C). The upperelectrode 522 is formed so as to overlap with the lower electrode withthe filler layer 519 therebetween. The first electrode 520, the wiring521, and the upper electrode 522 can be formed using a conductive metalor a semiconductor material, such as titanium, molybdenum, tantalum,chromium, tungsten, aluminum, neodymium, copper, silver, gold, platinum,niobium, silicon, zinc, iron, barium, or germanium; or an alloy materialthereof with sputtering, CVD, or the like.

A partition wall 523 which covers an end portion of the first electrode520 and has an opening reaching the upper electrode 522 is formed (seeFIG. 25C). For the partition wall 523, an organic resin film, aninorganic resin film, or an organic polysiloxane can be used.Specifically, the partition wall 523 is preferably formed usingpolyimide, polyamide, polyimide amide, acrylic, or abenzocyclobutene-based resin. It is particularly preferable that thepartition wall 523 be formed using a photosensitive material to have anopening over the first electrode 520 and the upper electrode 522 so thata sidewall of the opening is formed as a tilted surface with continuouscurvature.

A spacer 524 is formed so as to fill the opening in the partition wall523 reaching the upper electrode 522 (see FIG. 25C). An ultravioletcurable resin or the like can be used for the spacer 524. Specifically,the spacer 524 may be formed using an ultraviolet curable acrylic resinor the like. Note that the spacer 524 is formed so as to overlap withthe lower electrode 516.

Here, among the materials used for the filler layer 519, the partitionwall 523, and the spacer 524, the material used for the spacer 524 isthe hardest material and the material used for the filler layer 519 isthe softest material. Elastic modulus or the like indicates hardness orsoftness. The elastic modulus is a physical value indicating an object'stendency to be deformed elastically. In the case where hardness orsoftness is indicated by elastic modulus, the elastic modulus of thematerial used for the spacer 524 is higher than the elastic modulus ofthe material used for the partition wall 523, and the elastic modulus ofthe material used for the partition wall 523 is higher than the elasticmodulus of the material used for the filler layer 519.

An EL layer 525 is formed over the first electrode 520 (see FIG. 25C).The EL layer 525 includes a hole injection layer, a hole transportlayer, a light-emitting layer, an electron transport layer, an electroninjection layer, a hole blocking layer, and the like. The material usedfor the EL layer 525 may be selected as appropriate.

A second electrode 526 is formed over the EL layer 525 and the partitionwall 523 (see FIG. 25C). The first electrode 520, the EL layer 525, andthe second electrode 526 are included in a light-emitting element. Thesecond electrode 526 can be formed using a light-transmitting conductivematerial. As the light-transmitting conductive material, indium tinoxide (hereinafter referred to as ITO), indium oxide containing tungstenoxide, indium zinc oxide containing tungsten oxide, indium oxidecontaining titanium oxide, indium tin oxide containing titanium oxide,indium zinc oxide, indium tin oxide to which silicon oxide is added, orthe like can be used. The film formed using the light-transmittingconductive material may be formed with sputtering, CVD, or the like;however, this embodiment is not limited to a particular method. Further,the second electrode 526 may have either a single-layer structure or alayered structure.

Through the above steps, an element substrate can be formed. Then,sealing is performed in such a manner that a sealant (not illustrated)is provided at an end portion of the element substrate and the elementsubstrate and a sealing substrate 527 are attached to each other withthe sealant (see FIG. 26). The touch panel which is one embodiment ofthe present invention has a structure where a light-emitting element isprovided in a space 528 surrounded by the element substrate, the sealingsubstrate 527, and the sealant. The space 528 is filled with an inertgas (e.g., nitrogen or argon). The space 528 may be filled with asealant as a substitute for the inert gas.

Note that an epoxy-based resin is preferably used for the sealant. Inaddition, it is preferable to use a material which does not transmitmoisture or oxygen as much as possible. Further, as the sealingsubstrate 527, a glass substrate, a plastic substrate formed usingfiberglass-reinforced plastics (FRP), polyvinyl fluoride (PVF),polyester, acrylic, or the like can be used.

Next, FIG. 27 illustrates the case where the touch panel is touched witha finger.

As illustrated in FIG. 27, when the sealing substrate 527 is touchedwith a finger 529, the sealing substrate 527 bends. In this case, anupper portion of the partition wall 523 is pressed and dented, and thespacer 524 which is harder (which has higher elastic modulus) than thematerial used for the partition wall 523 is pressed down. Since thefiller layer 519 provided below the spacer 524 is softer (has lowerelastic modulus) than the spacer 524, the spacer 524 is pressed downwithout deformation. The upper electrode 522 of the microstructure(MEMS) is pressed down when the spacer 524 is pressed down. In the caseof the capacitive type touch panel, the distance between the lowerelectrode 516 and the upper electrode 522 of the microstructure (MEMS)is changed. Thus, data can be input. In the case of the resistive typetouch panel, the lower electrode 516 and the upper electrode 522 of themicrostructure (MEMS) are in contact with each other. Thus, data can beinput.

According to one embodiment of the present invention, a touch sensor canbe formed in steps of forming a thin film transistor and alight-emitting element.

According to one embodiment of the present invention, a touch sensor anda light-emitting element are disposed, so that it is possible to providea thin touch panel with less degradation in image quality as compared tothe case where a touch sensor is provided above or below alight-emitting element.

According to one embodiment of the present invention, by using materialshaving different hardness for a filler layer, a partition wall, and aspacer, it is possible to provide a touch panel where data can be inputefficiently and pressure is not applied to a light-emitting elementeasily. Further, by providing a spacer above a touch sensor, durabilityand sensitivity of the touch sensor can be improved.

Note that this embodiment can be combined with the structure describedin any of the other embodiments in this specification as appropriate.

Embodiment 9

A touch panel according to one embodiment of the present invention canbe used in a variety of electronic devices. Examples of electronicdevices include a television set (also referred to as a television or atelevision receiver), a monitor of a computer or the like, a camera suchas a digital camera or a digital video camera, a digital photo frame, amobile phone handset (also referred to as a mobile phone or a mobilephone device), a portable game machine, a portable information terminal,electronic paper, an audio reproducing device, a large game machine suchas a pinball machine, and the like. Examples of such electronic devicesare illustrated in FIGS. 28A and 28B.

FIG. 28A illustrates an example of an e-book reader 600. For example,the e-book reader 600 includes two housings 601 and 602. The housings601 and 602 are combined with each other with a hinge 603 so that thee-book reader 600 can be opened and closed with the hinge 603 as anaxis. With such a structure, the e-book reader 600 can be operated likea paper book.

A display portion 604 is incorporated in the housing 601, and a displayportion 605 is incorporated in the housing 602. Each of the displayportions 604 and 605 includes a touch sensor which is one embodiment ofthe present invention. The display portions 604 and 605 may display oneimage or different images. In the case where the display portion 604 and605 display different images, for example, a display portion on theright side (the display portion 604 in FIG. 28A) can display text and adisplay portion on the left side (the display portion 605 in FIG. 28A)can display images.

FIG. 28A illustrates an example in which the housing 601 includes anoperation portion and the like. For example, the housing 601 includes apower source 606, operation keys 607, a speaker 608, and the like. Notethat a keyboard, a pointing device, or the like may be provided on asurface of the housing, on which the display portion is provided.Further, an external connection terminal (e.g., an earphone terminal, aUSB terminal, or a terminal which can be connected to a variety ofcables such as USB cables), a recording medium insertion portion, or thelike may be provided on a back surface or a side surface of the housing.Furthermore, the e-book reader 600 may function as an electronicdictionary.

Further, the e-book reader 600 may transmit and receive data wirelessly.Through wireless communication, desired book data or the like can bepurchased and downloaded from an electronic book server.

According to one embodiment of the present invention, it is possible toprovide a thin e-book reader with less degradation in image quality ascompared to the case where a touch sensor is provided above or below alight-emitting element.

Further, according to one embodiment of the present invention, by usingmaterials having different hardness for a filler layer, a partitionwall, and a spacer, it is possible to provide a touch panel where datacan be input efficiently and pressure is not applied to a light-emittingelement easily. Furthermore, by providing a spacer above a touch sensor,it is possible to provide an e-book reader which includes a touch sensorhaving high durability and high sensitivity.

FIG. 28B illustrates an example of a digital photo frame 700. Forexample, in the digital photo frame 700, a display portion 702 isincorporated in a housing 701. The display portion 702 can display avariety of images. For example, the display portion 702 can display datarelated to images photographed by a digital camera or the like, so thatthe digital photo frame 700 can function as a normal photo frame.

By employing the touch sensor which is one embodiment of the presentinvention, it is possible to provide a thin digital photo frame withless degradation in image quality as compared to the case where a touchsensor is provided above or below a light-emitting element.

Further, according to one embodiment of the present invention, by usingmaterials having different hardness for a filler layer, a partitionwall, and a spacer, it is possible to provide a touch panel where datacan be input efficiently and pressure is not applied to a light-emittingelement easily. Furthermore, by providing a spacer above a touch sensor,it is possible to provide a digital photo frame which includes a touchsensor having high durability and high sensitivity.

This application is based on Japanese Patent Application serial no.2009-128549 filed with Japan Patent Office on May 28, 2009, the entirecontents of which are hereby incorporated by reference.

What is claimed is:
 1. A touch panel comprising: a transistor over afirst substrate, the transistor comprising a gate electrode, asemiconductor layer, a source electrode and a drain electrode; aninsulating layer covering the transistor, the insulating layer having anopening, a filler layer filling the opening; a light-emitting elementcomprising a first electrode over the insulating layer, a light-emittinglayer over the first electrode and a second electrode over thelight-emitting layer; a first capacitor comprising a first lowerelectrode, an upper electrode and the filler layer between the firstlower electrode and the upper electrode; a second capacitor comprising asecond lower electrode, the upper electrode and the filler layer betweenthe first lower electrode and the upper electrode; and a spacer betweena second substrate and the first substrate, the spacer overlapping withthe filler layer and the upper electrode, wherein the first lowerelectrode and the second lower electrode are formed using the samematerial as the gate electrode, and wherein the upper electrode is overthe insulating layer and formed using the same material as the firstelectrode.
 2. The touch panel according to claim 1, wherein the firstelectrode is electrically connected to one of the source electrode andthe drain electrode, and wherein the upper electrode is electricallyconnected to the other of the source electrode and the drain electrode.3. The touch panel according to claim 1, further comprising a partitionwall covering an end portion of the first electrode, the first capacitorand the second capacitor, wherein the partition wall has an opening, andwherein the spacer is provided so as to fill the opening in thepartition wall.
 4. The touch panel according to claim 3, wherein thespacer is formed using a material which is harder than a material of thepartition wall, and wherein the partition wall is formed using amaterial which is harder than the material of the filler layer.
 5. Thetouch panel according to claim 1, wherein the filler layer is formedusing an elastic insulating material which can be reversibly deformed bya pressure.
 6. The touch panel according to claim 5, wherein the elasticinsulating material is one of an elastomer and a thermoplasticelastomer.
 7. The touch panel according to claim 1, wherein the fillerlayer is formed using a porous insulating material which can bereversibly deformed by a pressure.
 8. The touch panel according to claim7, wherein the porous insulating material is a block copolymer.
 9. Thetouch panel according to claim 1, wherein the semiconductor layercomprises an oxide semiconductor.
 10. The touch panel according to claim1, wherein the first electrode of the light-emitting element and theupper electrode are spaced from each other.
 11. A touch panelcomprising: a transistor over a first substrate, the transistorcomprising a gate electrode, a semiconductor layer, a source electrodeand a drain electrode; an insulating layer covering the transistor, theinsulating layer having an opening, a filler layer filling the opening;a light-emitting element comprising a first electrode over theinsulating layer, a light-emitting layer over the first electrode and asecond electrode over the light-emitting layer; a first capacitorcomprising a first lower electrode, an upper electrode and the fillerlayer between the first lower electrode and the upper electrode; asecond capacitor comprising a second lower electrode, the upperelectrode and the filler layer between the first lower electrode and theupper electrode; and a spacer between a second substrate and the firstsubstrate, the spacer overlapping with the filler layer and the upperelectrode, wherein the first lower electrode and the second lowerelectrode are formed using the same material as the source electrode andthe drain electrode, and wherein the upper electrode is over theinsulating layer and formed using the same material as the firstelectrode.
 12. The touch panel according to claim 11, wherein the firstlower electrode is electrically connected to a first wiring, and whereinthe second lower electrode is electrically connected to a second wiring.13. The touch panel according to claim 11, wherein the first electrodeis electrically connected to one of the source electrode and the drainelectrode, and wherein the upper electrode is electrically connected tothe other of the source electrode and the drain electrode.
 14. The touchpanel according to claim 11, further comprising a partition wallcovering an end portion of the first electrode, the first capacitor andthe second capacitor, wherein the partition wall has an opening, andwherein the spacer is provided so as to fill the opening in thepartition wall.
 15. The touch panel according to claim 14, wherein thespacer is formed using a material which is harder than a material of thepartition wall, and wherein the partition wall is formed using amaterial which is harder than the material of the filler layer.
 16. Thetouch panel according to claim 11, wherein the filler layer is formedusing an elastic insulating material which can be reversibly deformed bya pressure.
 17. The touch panel according to claim 16, wherein theelastic insulating material is one of an elastomer and a thermoplasticelastomer.
 18. The touch panel according to claim 11, wherein the fillerlayer is formed using a porous insulating material which can bereversibly deformed by a pressure.
 19. The touch panel according toclaim 18, wherein the porous insulating material is a block copolymer.20. The touch panel according to claim 11, wherein the semiconductorlayer comprises an oxide semiconductor.
 21. The touch panel according toclaim 11, wherein the first electrode of the light-emitting element andthe upper electrode are spaced from each other.